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Interacciones atmósfera-superficie en Marte: delta 17O mediciones de carbonato de ALH 84001 obtenidas de las
J Farquhar1, M H Thiemens, T Jackson
1Department of Chemistry, University of California San Diego, 92093-0356, USA. jfarquha@ucsd.edu
Science (New York, N.Y.)
|June 11, 1998
Resumen
El meteorito marciano ALH 84001 revela distintos depósitos de isótopos de oxígeno en la atmósfera de Marte y en el planeta de silicato. Esto sugiere que los procesos atmosféricos, como la foto descomposición del ozono, crearon anomalías isotópicas registradas en los minerales de carbonato.
Área de la Ciencia:
- Ciencias planetarias Ciencias planetarias.
- La geoquímica es la geoquímica.
- Astrobiología Astrobiología.
Sus antecedentes:
- Los meteoritos marcianos proporcionan muestras cruciales para la comprensión de la historia geológica y atmosférica de Marte.
- Los isótopos de oxígeno en los minerales son trazadores sensibles de los procesos planetarios y las condiciones ambientales.
Objetivo del estudio:
- Para investigar la composición isotópica de oxígeno del carbonato del meteorito marciano ALH 84001.1.
- Determinar si en Marte existieron distintos depósitos de isótopos de oxígeno durante la formación de carbonatos.
- Para explorar los posibles mecanismos de las anomalías de isótopos de oxígeno atmosférico en Marte.
Principales métodos:
- Análisis de las relaciones de isótopos de oxígeno (delta18O, delta17O, Delta17O) en el carbonato de ALH 84001.1.
- Comparación de los datos de isótopos de carbonato marciano con las reservas terrestres conocidas y potenciales de silicato marciano.
Principales resultados:
- Las mediciones de isótopos de oxígeno de carbonato (delta18O = 18,3 ± 0,4 ‰, delta17O = 10,3 ± 0,2 ‰, Delta17O = 0,8 ± 0,05 ‰) muestran fraccionamiento en relación con los minerales de silicato.
- Estos resultados apoyan la presencia de al menos dos depósitos distintos de isótopos de oxígeno en Marte en el momento de la formación de carbonato: la atmósfera y el planeta de silicato.
- Un mecanismo potencial para la anomalía atmosférica involucra CO2 y oxígeno excitado (O(1D)) de la fotodescomposición del ozono.
Conclusiones:
- Los datos de isótopos de oxígeno del carbonato ALH 84001 indican una evolución isotópica compleja de la atmósfera marciana.
- Las firmas isotópicas atmosféricas pueden transferirse a los minerales de superficie a través del intercambio de CO2-H2O y la precipitación mineral.
- Se requiere un sumidero de oxígeno empobrecido con 17O, posiblemente dentro del regolito marciano, para equilibrar las composiciones isotópicas observadas.
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